1. |
Irwan Simanullang, Nozomu Fujimoto, Preliminary study of the composite moderator concept in small high-temperature gas-cooled reactors, 日本原子力学会, 2023.09. |

2. |
Hai Quan Ho, Shimpei Hamamoto, Nozomu Fujimoto, Satoru Nagasumi, Minoru Goto, Etsuo Ishitsuka, Calculation of decay gamma spectrum of the HTTR after shutdown, 日本原子力学会 2021年春の年会, 2021.03. |

3. |
Hai Quan Ho, Nozomu Fujimoto, Shimpei Hamamoto, Satoru Nagasumi, Minoru Goto, Etsuo Ishitsuka, Development of a utility tool for auto-seeking critical control rod position of the high temperature engineering test reactor, 日本原子力学会2020年秋の大会, 2020.09. |

4. |
Hai Quan Ho, Nozomu Fujimoto, Shimpei Hamamoto, Toshiaki Ishii, Satoru Nagasumi, Etsuo Ishituka, Calculation of 3D neutron flux distribution in the HTTR using MCNP6, 日本原子力学会 2019年秋の大会, 2019.09. |

5. |
Hai Quan Ho, Hiroki Ishida, Shimpei Hamamoto, Toshiaki Ishii, Nozomu Fujimoto, Naoyuki Takaki, Etsuo Ishitsuka, Feasibility study of 99mTc production at HTTR using sublimation method, 日本原子力学会 2019年春の年会, 2019.03. |

6. |
Ho Hai Quan, Yuki Honda, Nozomu Fujimoto, Minoru Goto, Etsuo Ishituka, Impact of truncated coated fuel particles on neutronic characteristic of statistical geometry model in MVP code, 日本原子力学会 2017年秋の大会, 2017.09, This study investigated the impact of truncated coated fuel particles (CFPs) on neutronic characteristic of the fuel in a statistical geometry (STG) model. Calculation results showed that the truncated CFPs make the multiplication factor decrease by about 0.1 – 1.0 %∆k/k depended on packing fraction, uranium enrichment, and particle size.. |

7. |
Ho Hai Quan, Keisuke Morita, Yuki Honda, Nozomu Fujimoto, Shoji Takada, Benchmark Study on Realized Random Packing Model for Coated Fuel Particles of HTTR using MCNP6, 2017 International Congress on Advances in Nuclear Power Plants, 2017.04, The Coated Fuel Particle plays an important role in the excellent safety feature of the High Temperature Gas-cooled Reactor. However, the random distribution of CFPs also makes the simulation of HTGR fuel become more complicated. The Monte Carlo N-particle (MCNP) code is one of the most well-known codes for validation of nuclear systems; unfortunately, it does not provide an appropriate function to model a statistical geometry explicitly. In order to deal with the stochastic media, a utility program for the random model, namely Realized Random Packing (RRP), has been developed particularly for High Temperature engineering Test Reactor (HTTR). This utility program creates a number of random points in an annular geometry. Then, these random points will be used as the center coordinate of CFPs in the MCNP6 input file and therefore the actual random arrangement of CFPs can be simulated explicitly. First, a pin-cell calculation was carried out to validate the RRP by comparing with Statistical Geometry (STG) model of MVP code. After that, the comparison between the RRP model (MCNP) and STG model (MVP) was shown in whole core criticality calculation, not only for the annular core but also for the fully-loaded core. The comparison of numerical results showed that the RRP model and STG model differed insignificantly in the multiplication factor as expected, regardless of the pin-cell or whole core calculations. In addition, the RRP model did not make the calculation time increase a lot in comparison with the conventional regular model (uniform arrangement).. |

8. |
Yuki Honda, 藤本 望, Hiroaki Sawahata, Kazuhiro Sawa, Burn-up dependency of control rod position at zero power criticality in the High Temperature Engineering Test Reactor, 23rd International Conference on Nuclear Engineering(ICONE-23), 2015.05, The High Temperature Engineering Test Reactor (HTTR) is a block type fuel High Temperature Gas-cooled Reactor (HTGR) constructed in Japan, firstly. The operating data of the HTTR with burn-up is very important for developments of HTGRs. Many test data have been collected in the HTTR. Many tests are carried out in low power operation. On the other hand, the full power operation is not enough. There is a temperature distribution in a core in full power operation. The temperature distribution in a core makes it difficult to validate the calculation code. Additionally, it is difficult to measure core temperature in HTTR. On the other hands, the data of the control rod position at criticality at zero power have been measured at the beginning of each operation cycle and the temperature distribution in a core at zero power is uniform. Therefore, the data at zero power are suitable for confirm the characteristics of burn-up and validation of calculation code. In this study, the calculated control rod positions at zero power criticality with burn-up are compared with the experimental data with correlation of core temperature. The calculated results of criticality control rod position at zero power show good agreement to the experimental data. It means that calculated result shows appropriate decrease in uranium and accumulation in plutonium decrease in burnable absorber with burn-up.. |

9. |
Yuki Honda, 藤本 望, Hiroaki Sawahata, Kazuhiro Sawa, Improvement of cell model for control rod in reflector region of High Temperature Engineering Test Reactor, 23rd International Conference on Nuclear Engineering(ICONE-23), 2015.05, The High Temperature Engineering Test Reactor (HTTR) is a block type fuel High Temperature Gas-cooled Reactor. There are 32 control rods (16 pairs) in the HTTR. The 6 pairs of control rods are inserted into a core region and the others are inserted in a reflector region surrounding the core. The core temperature of the HTTR is too high to insert all control rods simultaneously at reactor scram near full power operation for keeping integrity of control rods metallic sleeve. Therefore, a two-step control rods insertion method for reactor scram is adopted. The reactivity inserted at the two-step control rod insertion method was measured at HTTR criticality tests. The calculated reactivity at the first- step showed larger underestimation than that of the second- step. On the other hand, calculated results of excess reactivity at the HTTR criticality tests showed good agree with tests. It is considered that a cell model for reflector region control rod is not suitable. Therefore, this paper focuses on a new cell model for control rods in a reflector region. In a previous control rod cell model, control rod is surrounded by fuel blocks only. The surrounding condition of the new cell model corresponds to the configuration around the reflector region control rod. The calculated reactivity at the first-step using the new cell model shows better results than previous calculation. It is considered that the new cell model brings appropriate neutron flux distribution around control rods in reflector region.. |